The present invention relates to a refrigeration system, and more particularly to a technique for reducing the amount of refrigerant remaining on the indoor side by trapping the refrigerant on the outdoor side when the system is shut down.
A refrigeration system known in the art having an outdoor unit and an indoor unit connected to each other via communication pipes is designed to trap the refrigerant on the outdoor unit side when refrigerant leakage is detected and when the system is shut down in order to prevent the refrigerant from leaking into the room. For example, Japanese Laid-Open Patent Publication No. 5-118720 discloses a refrigeration system which performs a pump down operation for trapping the refrigerant on the outdoor unit side in the event of refrigerant leakage.
A conventional refrigeration system which traps the refrigerant in the indoor unit will be described with reference to FIG. 12. The refrigeration system includes electromagnetic valves (108) and (109) along communication pipes (113) separately from stop valves (106) and (107) for closing an outdoor unit (111) before connecting the outdoor unit (111) and an indoor unit (112) to each other.
During a cooling operation, the refrigerant discharged from a compressor (101) circulates as it passes through a four-way switching valve (102), is condensed through an outdoor heat exchanger (103), depressurized through an electric expansion valve (104) and evaporated through an indoor heat exchanger (105), and then returns to the compressor (101) via the four-way switching valve (102). When the system is shut down, the electromagnetic valve (109) on the liquid side (the high pressure side) is first closed while leaving the compressor (101) operating. Thus, the pressure on the low pressure side of the refrigerant circuit gradually decreases, and a low pressure switch (114) is eventually activated to shut down the compressor (101). Simultaneously with the shut down of the compressor (101), the electromagnetic valve (108) on the gas side (the low pressure side) is closed to close the outdoor unit (111), thereby trapping the refrigerant in the outdoor unit (111). Through such a pump down operation, substantially no refrigerant exists in the indoor unit (112), thereby avoiding leakage of a large amount of refrigerant into the room.
On the other hand, during a heating operation, the refrigerant discharged from the compressor (101) circulates as it passes through the four-way switching valve (102), is condensed through the indoor heat exchanger (105), depressurized through the electric expansion valve (104) and evaporated through the outdoor heat exchanger (103), and then returns to the compressor (101) via the four-way switching valve (102). When the system is shut down, the state of the four-way switching valve (102) is first switched to another so as to change the circulation path of the refrigerant to that in the cooling operation described above. Then, an operation as the pump down operation in the cooling operation is performed.
However, in the conventional refrigeration system described above, it is necessary to provide the electromagnetic valves (108) and (109) respectively for the communication pipes (113) and (113), and these electromagnetic valves (108) and (109) cause an increase in the cost of the system.
Moreover, when performing the pump down operation in a heating operation, the four-way switching valve (102) needs to be switched before performing a refrigerant circulation operation as that in a cooling operation, which lowers the efficiency of the system and may even detract from the comfort in the room.
Especially, where a slightly flammable refrigerant such as R32 or R32/134a is used as the refrigerant, it is particularly desired that the refrigerant is confined in the outdoor unit when the system is shut down because there is a risk of ignition due to the combustion of the refrigerant.
The present invention has been made in view of the above and aims to provide a refrigeration system capable of trapping the refrigerant on the outdoor side while maintaining the high efficiency and the comfort.
In order to achieve the above-described object, the present invention is designed so that a refrigerant of an indoor unit is trapped in an outdoor unit without switching the circulation direction of the refrigerant discharged from a compressor when shutting down either a cooling operation or a heating operation.
Specifically, a refrigeration system according to the present invention includes: an outdoor unit (1) including a compressor (4), a flow path switching mechanism (5) for switching a circulation direction of a refrigerant discharged from the compressor (4), an outdoor heat exchanger (6), and an expansion valve (7) capable of being fully closed; an indoor unit (2) including an indoor heat exchanger (8); and a communication pipe (3) for connecting the outdoor unit (1) and the indoor unit (2) to each other, wherein: the outdoor unit (1) includes: a receiver (10) provided upstream of the expansion valve (7); a gas vent passageway (12) for connecting the receiver (10) and a downstream side pipe (24) of the expansion valve (7) to each other; gas vent opening/closing means (13) provided along the gas vent passageway (12); and a bridge circuit (11), wherein during a cooling operation, the bridge circuit (11) only allows a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the outdoor heat exchanger (6), to the receiver (10) and a refrigerant flow in such a direction as to lead the refrigerant, which has been depressurized through the expansion valve (7), to the indoor heat exchanger (8), and during a heating operation, the bridge circuit (11) only allows a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the indoor heat exchanger (8), to the receiver (10) and a refrigerant flow in such a direction as to lead the refrigerant, which has been depressurized through the expansion valve (7), to the outdoor heat exchanger (6); and the refrigeration system further includes control means (35) for, before shutting down the compressor (4), opening the gas vent opening/closing means (13) and closing the expansion valve (7) while the compressor (4) is left operating, and for closing the gas vent opening/closing means (13) upon subsequent shut down of the compressor (4).
With the above arrangement, either in a cooling operation or in a heating operation, the condensed refrigerant will be expanded through the expansion valve (7) after passing through the receiver (10). Moreover, the backflow of refrigerant running from the receiver (10) to the bridge circuit (11) is prevented. Therefore, when shutting down either of these operations, the refrigerant is trapped in the receiver (10) by closing the expansion valve (7) without switching the flow path switching mechanism (5).
Because the expansion valve (7) is closed before the compressor (4) is shut down, the refrigerant is trapped in the receiver (10). At this time, since the gas vent opening/closing means (13) is opened, the gas refrigerant in the receiver (10) is discharged through the gas vent passageway (12), whereby the liquid refrigerant is efficiently stored in the receiver (10). Then, when the compressor (4) is shut down based on a predetermined condition, the gas vent opening/closing means (13) is closed, and the receiver (10) and the vicinity thereof are enclosed with the refrigerant being trapped therein. In this way, the refrigerant is collected into the outdoor unit (1) while the backflow thereof into the indoor unit (2) is prevented, thereby reducing the amount of refrigerant remaining in the indoor unit (2). Note that the control means (35) may be configured so as to start its control operation based on a predetermined shut down instruction such as, for example, a shut down instruction from the user turning OFF the system, turning OFF of a thermostat, or activation of a protection device.
Note that while it is particularly preferred that the time when the gas vent opening/closing means (13) is closed is simultaneous with the shut down of the compressor (4), they may not be simultaneous. Thus, the gas vent opening/closing means (13) may be closed prior to the shut down of the compressor (4), or it may be closed after passage of a short period of time from the shut down of the compressor (4).
Another refrigeration system according to the present invention includes: an outdoor unit (1) including a compressor (4), a flow path switching mechanism (5) for switching a circulation direction of a refrigerant discharged from the compressor (4), an outdoor heat exchanger (6), and an expansion valve (7) capable of being fully closed; an indoor unit (2) including an indoor heat exchanger (8); and a communication pipe (3) for connecting the outdoor unit (1) and the indoor unit (2) to each other, wherein: the outdoor unit (1) includes: a receiver (10) provided upstream of the expansion valve (7); a gas vent passageway (12) for connecting the receiver (10) and a downstream side pipe (24) of the expansion valve (7) to each other; gas vent opening/closing means (13) provided along the gas vent passageway (12); and a bridge circuit (11), wherein during a cooling operation, the bridge circuit (11) only allows a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the outdoor heat exchanger (6), to the receiver (10) and a refrigerant flow in such a direction as to lead the refrigerant, which has been depressurized through the expansion valve (7), to the indoor heat exchanger (8), and during a heating operation, the bridge circuit (11) only allows a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the indoor heat exchanger (8), to the receiver (10) and a refrigerant flow in such a direction as to lead the refrigerant, which has been depressurized through the expansion valve (7), to the outdoor heat exchanger (6); auxiliary opening/closing means (36) which is always opened during a normal operation is provided on an outdoor side of a gas side pipe (26) extending from the indoor unit (2) to the flow path switching mechanism (5); and the refrigeration system further includes control means (35) for, before shutting down the compressor (4) in a cooling operation, opening the gas vent opening/closing means (13) and closing the expansion valve (7) while the compressor (4) is left operating, and for closing the gas vent opening/closing means (13) and the auxiliary opening/closing means (36) upon subsequent shut down of the compressor (4).
With the above arrangement, since the auxiliary opening/closing means (36) is closed upon shut down, the path on the outdoor heat exchanger (6) side of the auxiliary opening/closing means (36) is also enclosed, whereby the refrigerant is trapped not only in the receiver (10) but also in the outdoor heat exchanger (6) and the compressor (4). Therefore, the amount of refrigerant collected into the outdoor unit (1) increases, and the amount of refrigerant remaining in the indoor unit (2) is reduced.
Note that while the refrigerant tends not to flow out to the indoor side when the compressor (4) is a low pressure dome type compressor, the refrigerant tends to flow out to the indoor side when the compressor (4) is a high pressure dome type compressor, in which case the effect of providing the auxiliary opening/closing means (36) is more pronounced.
Another refrigeration system according to the present invention includes: an outdoor unit (1) including a compressor (4), a flow path switching mechanism (5) for switching a circulation direction of a refrigerant discharged from the compressor (4), an outdoor heat exchanger (6), and an expansion valve (7) capable of being fully closed; an indoor unit (2) including an indoor heat exchanger (8); and a communication pipe (3) for connecting the outdoor unit (1) and the indoor unit (2) to each other, wherein: the outdoor unit (1) includes: a receiver (10) provided upstream of the expansion valve (7); a gas vent passageway (12) for connecting the receiver (10) and a downstream side pipe (24) of the expansion valve (7) to each other; gas vent opening/closing means (13) provided along the gas vent passageway (12); and a bridge circuit (11), wherein during a cooling operation, the bridge circuit (11) only allows a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the outdoor heat exchanger (6), to the receiver (10) and a refrigerant flow in such a direction as to lead the refrigerant, which has been depressurized through the expansion valve (7), to the indoor heat exchanger (8), and during a heating operation, the bridge circuit (11) only allows a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the indoor heat exchanger (8), to the receiver (10) and a refrigerant flow in such a direction as to lead the refrigerant, which has been depressurized through the expansion valve (7), to the outdoor heat exchanger (6); auxiliary opening/closing means (36) which is always opened during a normal operation is provided on an outdoor side of a gas side pipe (26) extending from the indoor unit (2) to the flow path switching mechanism (5); the refrigeration system further includes temperature difference detection means (37, 38) for detecting a temperature difference between an indoor side and an outdoor side; and the refrigeration system further includes control means (35) for, before shutting down the compressor (4) in a heating operation, opening the gas vent opening/closing means (13) and closing the expansion valve (7) while the compressor (4) is left operating, and for closing the gas vent opening/closing means (13) and the auxiliary opening/closing means (36) when an outdoor temperature becomes equal to or greater than an indoor temperature after subsequent shut down of the compressor (4).
With the above arrangement, before the compressor (4) is shut down, the gas vent opening/closing means (13) is opened and the expansion valve (7) is closed, whereby the refrigerant is efficiently trapped in the receiver (10). Then, even after the compressor (4) is shut down, the refrigerant of the indoor unit (2) flows into the outdoor unit (1) if the indoor temperature is higher than the outdoor temperature. Therefore, in order to further collect the refrigerant of the indoor unit (2) into the outdoor unit (1), the gas vent opening/closing means (13) and the auxiliary opening/closing means (36) are left open. Then, when the outdoor temperature becomes equal to or greater than the indoor temperature, the gas vent opening/closing means (13) and the auxiliary opening/closing means (36) are closed so as to enclose the refrigerant in the receiver (10), the outdoor heat exchanger (6), the compressor (4) and the pipes connecting these elements to one another.
The auxiliary opening/closing means (36) may be configured so that the auxiliary opening/closing means (36) can be manually opened/closed, and may be used also as a stop valve (15) for closing the outdoor unit (1) before connecting the outdoor unit (1) to the indoor unit (2).
With the above arrangement, it is not necessary to separately provide the stop valve (15) for closing the outdoor unit (1) before connecting the outdoor unit (1) and the indoor unit (2) to each other, thereby reducing the cost of the system.
Another refrigeration system according to the present invention includes a compressor (4), a flow path switching mechanism (5) for switching a circulation direction of a refrigerant discharged from the compressor (4), an outdoor heat exchanger (6), an expansion valve (7) capable of being fully closed, and an indoor heat exchanger (8), which are connected to one another by a refrigerant pipe, the refrigeration system further including: a receiver (10) provided upstream of the expansion valve (7); a gas vent passageway (12) for connecting the receiver (10) and a downstream side pipe (24) of the expansion valve (7) to each other; gas vent opening/closing means (13) provided along the gas vent passageway (12); and a bridge circuit (11), wherein during a cooling operation, the bridge circuit (11) only allows a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the outdoor heat exchanger (6), to the receiver (10) and a refrigerant flow in such a direction as to lead the refrigerant, which has been depressurized through the expansion valve (7), to the indoor heat exchanger (8), and during a heating operation, the bridge circuit (11) only allows a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the indoor heat exchanger (8), to the receiver (10) and a refrigerant flow in such a direction as to lead the refrigerant, which has been depressurized through the expansion valve (7), to the outdoor heat exchanger (6), wherein: at least the following elements are provided on an outdoor side: the receiver (10); a path (23) extending from the receiver (10) to the expansion valve (7); a path (K1) extending from a circuit section in the bridge circuit (11) to the receiver (10), the circuit section only allowing a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the outdoor heat exchanger (6), to the receiver (10) during a cooling operation; a path (K2) extending from a circuit section in the bridge circuit (11) to the receiver (10), the circuit section only allowing a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the indoor heat exchanger (8), to the receiver (10) during a heating operation; and a path (K3) along the gas vent passageway (12) extending from the receiver (10) to the gas vent opening/closing means (13); and the refrigeration system further includes control means (35) for, before shutting down the compressor (4), opening the gas vent opening/closing means (13) and closing the expansion valve (7) while the compressor (4) is left operating, and for closing the gas vent opening/closing means (13) upon subsequent shut down of the compressor (4).
With the above arrangement, the expansion valve (7) is closed before the compressor (4) is shut down, whereby the refrigerant is trapped in the receiver (10). At this time, since the gas vent opening/closing means (13) is opened, the gas refrigerant in the receiver (10) is discharged through the gas vent passageway (12), whereby the liquid refrigerant is efficiently stored in the receiver (10). Then, when the compressor (4) is shut down, the gas vent opening/closing means (13) is closed, and the refrigerant is trapped in the receiver (10) and the paths (23), (K1), (K2) and (K3). In this way, the refrigerant is collected to the outdoor side while the backflow thereof to the indoor side is prevented, thereby reducing the amount of refrigerant remaining on the indoor side.
Another refrigeration system according to the present invention includes a compressor (4), a flow path switching mechanism (5) for switching a circulation direction of a refrigerant discharged from the compressor (4), an outdoor heat exchanger (6), an expansion valve (7) capable of being fully closed, and an indoor heat exchanger (8), which are connected to one another by a refrigerant pipe, the refrigeration system further including: a receiver (10) provided upstream of the expansion valve (7); a gas vent passageway (12) for connecting the receiver (10) and a downstream side pipe (24) of the expansion valve (7) to each other; gas vent opening/closing means (13) provided along the gas vent passageway (12); a bridge circuit (11), wherein during a cooling operation, the bridge circuit (11) only allows a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the outdoor heat exchanger (6), to the receiver (10) and a refrigerant flow in such a direction as to lead the refrigerant, which has been depressurized through the expansion valve (7), to the indoor heat exchanger (8), and during a heating operation, the bridge circuit (11) only allows a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the indoor heat exchanger (8), to the receiver (10) and a refrigerant flow in such a direction as to lead the refrigerant, which has been depressurized through the expansion valve (7), to the outdoor heat exchanger (6); and auxiliary opening/closing means (36) provided on an outdoor side of a gas side pipe (26) extending from indoor heat exchanger (8) to the flow path switching mechanism (5), the auxiliary opening/closing means (36) being always opened during a normal operation, wherein: at least the following elements are provided on an outdoor side: the receiver (10); a path (23) extending from the receiver (10) to the expansion valve (7); a path (K1) extending from a circuit section in the bridge circuit (11) to the receiver (10), the circuit section only allowing a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the outdoor heat exchanger (6), to the receiver (10) during a cooling operation; a path (K2) extending from a circuit section in the bridge circuit (11) to the receiver (10), the circuit section only allowing a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the indoor heat exchanger (8), to the receiver (10) during a heating operation; a path (K3) along the gas vent passageway (12) extending from the receiver (10) to the gas vent opening/closing means (13); and a path (k4) extending from the outdoor heat exchanger (6) to the auxiliary opening/closing means (36); and the refrigeration system further includes control means (35) for, before shutting down the compressor (4), opening the gas vent opening/closing means (13) and closing the expansion valve (7) while the compressor (4) is left operating, and for closing the gas vent opening/closing means (13) and the auxiliary opening/closing means (36) upon subsequent shut down of the compressor (4).
With the above arrangement, since the auxiliary opening/closing means (36) is closed upon shut down, the path on the outdoor heat exchanger (6) side of the auxiliary opening/closing means (36) is also enclosed, whereby the refrigerant is trapped not only in the receiver (10) but also in the outdoor heat exchanger (6) and the compressor (4). Therefore, the amount of refrigerant collected to the outdoor side increases, and the amount of refrigerant remaining on the indoor side is reduced.
Another refrigeration system according to the present invention includes a compressor (4), a flow path switching mechanism (5) for switching a circulation direction of a refrigerant discharged from the compressor (4), an outdoor heat exchanger (6), an expansion valve (7) capable of being fully closed, and an indoor heat exchanger (8), which are connected to one another by a refrigerant pipe, the refrigeration system further including: a receiver (10) provided upstream of the expansion valve (7); a gas vent passageway (12) for connecting the receiver (10) and a downstream side pipe (24) of the expansion valve (7) to each other; gas vent opening/closing means (13) provided along the gas vent passageway (12); a bridge circuit (11), wherein during a cooling operation, the bridge circuit (11) only allows a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the outdoor heat exchanger (6), to the receiver (10) and a refrigerant flow in such a direction as to lead the refrigerant, which has been depressurized through the expansion valve (7), to the indoor heat exchanger (8), and during a heating operation, the bridge circuit (11) only allows a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the indoor heat exchanger (8), to the receiver (10) and a refrigerant flow in such a direction as to lead the refrigerant, which has been depressurized through the expansion valve (7), to the outdoor heat exchanger (6); auxiliary opening/closing means (36) provided on an outdoor side of a gas side pipe (26) extending from indoor heat exchanger (8) to the flow path switching mechanism (5), the auxiliary opening/closing means (36) being always opened during a normal operation; and temperature difference detection means (37, 38) for detecting a temperature difference between an indoor side and an outdoor side, wherein: at least the following elements are provided on an outdoor side: the receiver (10); a path (23) extending from the receiver (10) to the expansion valve (7); a path (K1) extending from a circuit section in the bridge circuit (11) to the receiver (10), the circuit section only allowing a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the outdoor heat exchanger (6), to the receiver (10) during a cooling operation; a path (K2) extending from a circuit section in the bridge circuit (11) to the receiver (10), the circuit section only allowing a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the indoor heat exchanger (8), to the receiver (10) during a heating operation; a path (K3) along the gas vent passageway (12) extending from the receiver (10) to the gas vent opening/closing means (13); and a path (k4) extending from the outdoor heat exchanger (6) to the auxiliary opening/closing means (36); and the refrigeration system further includes control means (35) for, before shutting down the compressor (4) in a heating operation, opening the gas vent opening/closing means (13) and closing the expansion valve (7) while the compressor (4) is left operating, and for closing the gas vent opening/closing means (13) and the auxiliary opening/closing means (36) when an outdoor temperature becomes equal to or greater than an indoor temperature after subsequent shut down of the compressor (4).
With the above arrangement, before the compressor (4) is shut down, the gas vent opening/closing means (13) is opened and the expansion valve (7) is closed, whereby the refrigerant is efficiently trapped in the receiver (10). Then, even after the compressor (4) is shut down, the refrigerant on the indoor side flows to the outdoor side if the indoor temperature is higher than the outdoor temperature. Therefore, in order to further collect the refrigerant on the indoor side to the outdoor side, the gas vent opening/closing means (13) and the auxiliary opening/closing means (36) are left open. Then, when the outdoor temperature becomes equal to or greater than the indoor temperature, the gas vent opening/closing means (13) and the auxiliary opening/closing means (36) are closed so as to enclose the refrigerant in the receiver (10), the outdoor heat exchanger (6), the compressor (4) and the paths.
Another refrigeration system according to the present invention includes a compressor (4), a flow path switching mechanism (5) for switching a circulation direction of a refrigerant discharged from the compressor (4), an outdoor heat exchanger (6), an expansion valve (7) capable of being fully closed, and an indoor heat exchanger (8), which are connected to one another by a refrigerant pipe, the refrigeration system further including: a receiver (10) provided upstream of the expansion valve (7); a gas vent passageway (12) for connecting the receiver (10) and a downstream side pipe (24) of the expansion valve (7) to each other; gas vent opening/closing means (13) provided along the gas vent passageway (12); a bridge circuit (11), wherein during a cooling operation, the bridge circuit (11) only allows a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the outdoor heat exchanger (6), to the receiver (10) and a refrigerant flow in such a direction as to lead the refrigerant, which has been depressurized through the expansion valve (7), to the indoor heat exchanger (8), and during a heating operation, the bridge circuit (11) only allows a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the indoor heat exchanger (8), to the receiver (10) and a refrigerant flow in such a direction as to lead the refrigerant, which has been depressurized through the expansion valve (7), to the outdoor heat exchanger (6); auxiliary opening/closing means (36) provided on an outdoor side of a gas side pipe (26) extending from indoor heat exchanger (8) to the flow path switching mechanism (5), the auxiliary opening/closing means (36) being always opened during a normal operation; and an outdoor fan (9) for supplying an air to the outdoor heat exchanger (6), wherein: at least the following elements are provided on an outdoor side: the receiver (10); a path (23) extending from the receiver (10) to the expansion valve (7); a path (K1) extending from a circuit section in the bridge circuit (11) to the receiver (10), the circuit section only allowing a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the outdoor heat exchanger (6), to the receiver (10) during a cooling operation; a path (K2) extending from a circuit section in the bridge circuit (11) to the receiver (10), the circuit section only allowing a refrigerant flow in such a direction as to lead the refrigerant, which has been condensed through the indoor heat exchanger (8), to the receiver (10) during a heating operation; a path (K3) along the gas vent passageway (12) extending from the receiver (10) to the gas vent opening/closing means (13); and a path (k4) extending from the outdoor heat exchanger (6) to the auxiliary opening/closing means (36); and the refrigeration system further includes control means (35) for, before shutting down the compressor (4) in a heating operation, opening the gas vent opening/closing means (13) and closing the expansion valve (7) while the compressor (4) is left operating, for closing the auxiliary opening/closing means (36) upon subsequent shut down of the compressor (4), and for closing the gas vent opening/closing means (13) upon shut down of the outdoor fan (9).
With the above arrangement, before the compressor (4) is shut down, the gas vent opening/closing means (13) is opened and the expansion valve (7) is closed, whereby the refrigerant is efficiently trapped in the receiver (10). Then, when the compressor (4) is shut down, the auxiliary opening/closing means (36) is closed. Since the refrigerant is condensed through the outdoor heat exchanger (6) while the outdoor fan (9) is left operating, and the gas vent opening/closing means (13) is opened, the refrigerant on the indoor side flows to the outdoor side through the gas vent passageway (12). Therefore, the amount of refrigerant collected to the outdoor side increases. Then, upon shut down of the outdoor fan (9), the gas vent opening/closing means (13) is closed, whereby the refrigerant is enclosed in the receiver (10), the outdoor heat exchanger (6), the compressor (4) and the paths.
The bridge circuit (11) may include: a first check valve (31) for allowing only a refrigerant flow running in a direction from a first connection terminal (11a) connected to the outdoor heat exchanger (6) to a second connection terminal (11b) connected to the receiver (10); a second check valve (32) for allowing only a refrigerant flow running in a direction from a third connection terminal (11c) connected to the indoor heat exchanger (8) to the second connection terminal (11b); a third check valve (33) for allowing only a refrigerant flow running in a direction from a fourth connection terminal (11d) connected to a downstream side pipe (24) of the expansion valve (7) to the third connection terminal (11c); and a fourth check valve (34) for allowing only a refrigerant flow running in a direction from the fourth connection terminal (11d) to the first connection terminal (11a).
With the above arrangement, during a cooling operation, the refrigerant, which has been condensed through the heat exchanger (6), passes through the first check valve (31) and flows into the receiver (10), and the refrigerant, which has been depressurized through the expansion valve (7), passes through the third check valve (33) and is evaporated through the indoor heat exchanger (8). During a heating operation, the refrigerant, which has been condensed through the indoor heat exchanger (8), passes through the second check valve (32) and flows into the receiver (10), and the refrigerant, which has been depressurized through the expansion valve (7), passes through the fourth check valve (34) and is evaporated through the outdoor heat exchanger (6). In either operation, the backflow of refrigerant from the receiver (10) is prevented by the first check valve (31) and the second check valve (32), and by closing the expansion valve (7) and the gas vent opening/closing means (13), the receiver (10) and the vicinity thereof are enclosed, thereby trapping the refrigerant therein.
The flow path switching mechanism (5) may be an electric ball-valve-type four-way switching valve (5A).
With the above arrangement, the refrigerant leakage between the high pressure side and the low pressure side is considerably reduced, whereby it is possible to reliably prevent the refrigerant, which has once been trapped on the outdoor side, from being discharged to the indoor side.
Another refrigeration system according to the present invention includes a compressor (4), an outdoor heat exchanger (6), an expansion valve (7) capable of being fully closed, and an indoor heat exchanger (8), which are connected to one another by a refrigerant pipe, the refrigeration system further including: a receiver (10) provided upstream of the expansion valve (7); a gas vent passageway (12) for connecting the receiver (10) and a downstream side pipe (24) of the expansion valve (7) to each other; gas vent opening/closing means (13) provided along the gas vent passageway (12); and backflow preventing means (31) provided upstream of the receiver (10) for allowing only a refrigerant flow running from the outdoor heat exchanger (6) to the receiver (10), wherein: at least a path extending from the backflow preventing means (31) to the expansion valve (7) via the receiver (10), and a path along the gas vent passageway (12) extending from the receiver (10) to the gas vent opening/closing means (13) are provided on an outdoor side; and the refrigeration system further includes control means (35) for, before shutting down the compressor (4), opening the gas vent opening/closing means (13) and closing the expansion valve (7) while the compressor (4) is left operating, and for closing the gas vent opening/closing means (13) upon subsequent shut down of the compressor (4).
With the above arrangement, even in a refrigeration system that does not require a bridge circuit such as, for example, a cooling only system, the refrigerant is effectively trapped on the outdoor side by opening/closing the gas vent opening/closing means (13).
Another refrigeration system according to the present invention includes a compressor (4), an outdoor heat exchanger (6), an expansion valve (7) capable of being fully closed, and an indoor heat exchanger (8), which are connected to one another by a refrigerant pipe, the refrigeration system further including: a receiver (10) provided upstream of the expansion valve (7); a gas vent passageway (12) for connecting the receiver (10) and a downstream side pipe (24) of the expansion valve (7) to each other; gas vent opening/closing means (13) provided along the gas vent passageway (12); and auxiliary opening/closing means provided upstream of the receiver (10), the auxiliary opening/closing means being always opened during a normal operation, wherein: at least a path extending from the auxiliary opening/closing means to the expansion valve (7) via the receiver (10), and a path along the gas vent passageway (12) extending from the receiver (10) to the gas vent opening/closing means (13) are provided on an outdoor side; and the refrigeration system further includes control means (35) for, before shutting down the compressor (4), opening the gas vent opening/closing means (13) and closing the expansion valve (7) while the compressor (4) is left operating, and for closing the gas vent opening/closing means (13) and the auxiliary opening/closing means upon subsequent shut down of the compressor (4).
With the above arrangement, even in a refrigeration system that does not require a bridge circuit such as, for example, a cooling only system, the refrigerant is effectively trapped on the outdoor side by opening/closing the gas vent opening/closing means (13) and the auxiliary opening/closing means.
Backflow preventing means (46) for allowing only a refrigerant flow in a direction in which the refrigerant is discharged from the compressor (4) may be provided on a discharge side of the compressor (4).
With the above arrangement, the downstream side of the check valve (46) is also closed upon shut down, whereby the refrigerant is trapped not only in the receiver (10) but also in the outdoor heat exchanger (6). Therefore, the amount of refrigerant collected to the outdoor side increases, and the amount of refrigerant remaining on the indoor side is reduced.
Backflow preventing means (46) for allowing only a refrigerant flow in a direction in which the refrigerant is sucked into the compressor (4) may be provided on a suction side of the compressor (4).
With the above arrangement, the upstream side of the check valve (46) is also closed upon shut down, whereby the refrigerant is trapped not only in the receiver (10) but also in the outdoor heat exchanger (6) and the compressor (4). Therefore, the amount of refrigerant collected to the outdoor side increases, and the amount of refrigerant remaining on the indoor side is reduced.
The auxiliary opening/closing means (36) may be an electric ball valve (40).
With the above arrangement, the pressure loss of the refrigerant at the auxiliary opening/closing means (36) is reduced, thereby improving the efficiency of collecting the refrigerant.
The control means (35) may be configured so as to shut down the compressor (4) when a fully closed state of the expansion valve (7) has continued for a predetermined period of time.
With the above arrangement, since the compressor (4) is shut down based on the amount of time for which the expansion valve (7) is fully closed, the control operation is simplified.
A low pressure switch (30) may be provided along a suction side pipe (28) of the compressor (4); and the control means (35) may be configured so as to shut down the compressor (4) when the low pressure switch (30) is activated.
With the above arrangement, since the compressor (4) is shut down based on activation of the low pressure switch (30), the refrigerant of the indoor unit (2) is reliably collected and the control operation is simplified.
Note that the refrigerant may include a flammable refrigerant. The term xe2x80x9cflammable refrigerantxe2x80x9d as used herein includes an HC-based refrigerant such as propane and a slightly flammable refrigerant such as HFC32.
With the above arrangement, since such a refrigerant including a flammable refrigerant necessitates a strict refrigerant leakage control, the effect of trapping a large amount of refrigerant on the outdoor side is more pronounced.
As described above, according to the present invention, the refrigerant can be efficiently trapped on the outdoor side only by closing the expansion valve without switching the flow path switching mechanism. Moreover, the refrigerant can be efficiently trapped in the receiver by leaving open the gas vent opening/closing means provided along the gas vent passageway starting from the shut down of the system until the shut down of the compressor. Therefore, it is possible to reduce the amount of refrigerant remaining on the indoor side. Moreover, even in the case of a system that is not provided with a flow path switching mechanism, the refrigerant can be effectively trapped on the outdoor side by providing the backflow preventing means on the upstream side of the receiver.
Where the backflow preventing means is provided on the discharge side or the suction side of the compressor, the downstream side of the backflow preventing means is also closed upon shut down, whereby the refrigerant can be trapped not only in the receiver but also in the outdoor heat exchanger. As a result, it is possible to further reduce the amount of refrigerant remaining on the indoor side.
Where the auxiliary opening/closing means which is always opened during a normal operation is provided, a section extending on the outdoor heat exchanger side of the auxiliary opening/closing means is also enclosed, whereby the refrigerant can be trapped not only in the receiver but also in the outdoor heat exchanger and the compressor. Therefore, it is possible to increase the amount of refrigerant collected to the outdoor side and to further reduce the amount of refrigerant remaining on the indoor side.
Where the auxiliary opening/closing means is configured so that it can be manually opened/closed, and is used also as the stop valve, it is not necessary to separately provide the stop valve, thereby reducing the cost of the system.
Where the auxiliary opening/closing means is an electric ball valve, the pressure loss of the refrigerant is reduced, thereby improving the efficiency of collecting the refrigerant.
Where the flow path switching mechanism is an electric ball-valve-type four-way switching valve, the refrigerant leakage between the high pressure side and the low pressure side is considerably reduced, whereby it is possible to reliably prevent the refrigerant, which has once been trapped on the outdoor side, from being discharged to the indoor side.
Where there is provided control means for, before shutting down the compressor, opening the gas vent opening/closing means and closing the expansion valve while the compressor is left operating, and for closing the gas vent opening/closing means and the auxiliary opening/closing means upon subsequent shut down of the compressor, the refrigerant on the indoor side flows to the outdoor side through the gas vent passageway even after the shut down of the compressor, whereby a large amount of refrigerant can be enclosed in the receiver, the outdoor heat exchanger, the compressor and the pipes connecting these elements to one another.
Where there is provided control means for, before shutting down the compressor in a heating operation, opening the gas vent opening/closing means and closing the expansion valve while the compressor is left operating, and for closing the gas vent opening/closing means and the auxiliary opening/closing means when the outdoor temperature becomes equal to or greater than the indoor temperature after subsequent shut down of the compressor, the natural circulation of the refrigerant can be maximally utilized, whereby it is possible to further increase the amount of refrigerant to be collected to the outdoor side.
Where an expansion valve capable of being fully closed is used, and the control means is configured so as to shut down the compressor when the fully closed state of the expansion valve has continued for a predetermined period of time, the refrigerant can be collected smoothly and the control operation can be simplified.
Where an expansion valve capable of being fully closed is used, with a low pressure switch being provided along the suction side pipe of the compressor, and the control means being configured so as to shut down the compressor when the low pressure switch is activated, the refrigerant can be collected smoothly, and since the compressor is shut down based on activation of the low pressure switch, the reliable collection of the indoor side refrigerant is facilitated and the control operation can be simplified.
Note that where a refrigerant including a flammable refrigerant is used, the various effects described above are more pronounced.